[1] Univ Penn, Palliat & Adv Illness Res Ctr, Perelman Sch Med, Philadelphia, PA 19104 USA
[2] Univ Penn, Dept Biostat Epidemiol & Informat, Perelman Sch Med, 719 Blockley Hall,423 Guardian Dr, Philadelphia, PA 19104 USA
[3] Philadelphia VA Med Ctr, Ctr Hlth Equ Res & Promot, Philadelphia, PA USA
[4] Univ Penn, Leonard Davis Inst Hlth Econ, Philadelphia, PA 19104 USA
[5] Univ Penn, Dept Med, Perelman Sch Med, Div Pulm Allergy & Crit Care Med, Philadelphia, PA 19104 USA
[6] Univ Penn, Dept Med Eth & Hlth Policy, Perelman Sch Med, Philadelphia, PA 19104 USA